FISH-CULTURAL PRACTICES IN THE BUREAU OF FISHERIES. 729 



the new bank on the south side of the stream. The logs were let down through 

 the dam foundation to low-water level on the north side and the deep channel 

 under them on the south side was filled with brush and gravel. The logs were 

 spotted down to form a practically level bed, reaching the width of the stream. 

 Heavy piles were then driven behind each stringer to form alternate single and 

 double rows extending up and down stream. The log stringers were next 

 planked over, forming a platform 18 feet wide, similar to a regular dam apron, 

 extending from the north abutment to the final row of piles on the south side, 

 a distance of about 140 feet. 



By planking the sides of the single rows of piles and all around the double 

 rows and filling the space with rocks, piers 4 feet high and approximately 2 feet 

 and 4 feet wide were formed. Through each pier at the bottom, behind the 

 upstream pile, openings i foot square were left, connecting the spaces between 

 the piers. These spaces, 12 in number, are approximately 8 feet wide and are 

 filled by swinging gates hinged to a 3 by 1 2 inch timber, spiked securely to the 

 piers on either side and forming a dam or flashboard across the space above. 

 By the insertion of other flashboards above this one a tight dam 4 feet high 

 can be quickly formed at any time. The utility of this feature will be explained 

 elsewhere. 



The gates are made of i by 4 inch fir set on edge and nailed to 2 by 4 inch 

 joist, being strengthened by 2-inch blocks set between the rack bars and nailed 

 to them and the joists. These blocks thus determine the width of the inter- 

 stices in the gates. At the upper end of each gate an auger hole is bored 

 through the bars and blocks, to accommodate a 2-inch iron pipe, which passes 

 through the entire upper end of the gates. Ringbolts clasp these pipes and 

 are fastened to the 3 by 12 inch timber forming the flashboard, acting as hinges 

 upon which the gates swing. At the lower end of each gate a wide board, 

 iX by 16 inches, is secured by means of braces, forming an angle of 45° with 

 the lower end of the gate. 



At any ordinary stage of the stream the downstream ends of the gates 

 rest on supports which hold them a foot or more higher than the upper ends, 

 the water passing down through them to the floor of the apron, where it runs 

 away. The fish working up under the gates to the dam board find the cross 

 passages through the front end of the piers and finally reach the trap. It was 

 expected that during freshets the current acting on the flashboard would 

 always keep the lower ends of the gates above the surface of the water, and 

 up to a certain point this expectation was realized, but at very high stages of 

 the stream the large quantity of gravel in the water soon clogs and sinks the 

 gates. As the gates are only two-thirds the length of the apron, however, and 

 rise toward the lower end, the water shoots over them with such force that it 

 is projected some distance below the end of the apron, and fish attempting to 



B. B. F. 190S— Pt 2—4 



